The present invention relates generally to electronic solid state and integrated circuit devices. More specifically, the present invention relates to apparatuses for dissipating heat generated by such devices. In addition, the present invention relates to cooling of multiple heat generating electronic devices with a single heat sink assembly.
In the electronics and computer industries, it has been well known to employ various types of electronic device packages and integrated circuit chips, such as the PENTIUM central processing unit chip (CPU) manufactured by Intel Corporation and RAM (random access memory) chips. These integrated circuit chips have a pin grid array (PGA) package and are typically installed into a socket which is soldered to a computer circuit board. These integrated circuit devices, particularly the CPU microprocessor chips, generate a great deal of heat during operation which must be removed to prevent adverse effects on operation of the system into which the device is installed. For example, a PENTIUM microprocessor, containing millions of transistors, is highly susceptible to overheating which could destroy the microprocessor device itself or other components proximal to the microprocessor.
In addition to the PENTIUM microprocessor discussed above, there are many other types of semiconductor device packages which are commonly used in computer equipment, for example. Recently, various types of surface mount packages, such as BGA (ball grid array) and LGA (land grid array) type semiconductor packages have become increasingly popular as the semiconductor package of choice for computers.
Also, it is very common in the electronics industry to many electronic devices on a single circuit board, such as a motherboard, modem, or xe2x80x9cprocessor cardxe2x80x9d such as the Celeron board manufactured by Intel Corporation. Many times, a number of these electronic devices suffer from over heating in similar fashion to the devices discussed above. If such heat is not properly dissipated from these devices, the device or component will eventually fail or cease to operate properly. For example, a number of electronic devices may be installed proximal to one another in a cluster on a particular region on a circuit board. If each of these devices require cooling to avoid failure, some type of heat dissipation is necessary.
In the prior art, it has been common to provide xe2x80x9cbulkxe2x80x9d cooling to a group of devices that require heat dissipation. In these devices, a single heat sink is placed over all of the devices that required cooling. For example, a block heat sink with a base with a flat bottom and upstanding pins, is dimensioned large enough to rest on the top heat generating surfaces of each of the heat generating devices. In this prior art assembly, the base of the heat sink member is affixed to the top surfaces of the devices to be cooled by a thermally conductive epoxy, thermally conductive double-side tape, and the like. As a result, a single heat sink member may simultaneously provide heat dissipating for a number of devices.
The foregoing prior art assembly is generally acceptable when all of the devices to be cooled have the same thickness or if their top surfaces lie in the same plane. This is required so that the block heat sink base may sit flush on the top surfaces for proper thermal transfer. Modifications to this general prior art assembly have been made for the block heat sink to specifically accommodate multiple devices that are of different heights or have top surfaces that do not lie in the same plane. In particular, highly compressible thermally conductive gap pads or gap filler materials are commonly used to fill the gaps between the bottom of the heat sink and the top surfaces of the devices to be cooled. For example, if a device is shorter than other devices in the group of devices to be cooled, the gap pad expands so as to fill the void between to bottom of the heat sink and the top of the device to bridge the thermal gap for that shorter device. This enables thermal transfer to the shorter device. Gap pads of the prior art are simply affixed to the heat sink and top surfaces by thermally conductive epoxy, or the like, and/or the entire assembly may be secured together by mechanical structures, such as clamps or fasteners.
The foregoing heat sink assemblies of the prior art suffer from the disadvantages employing a large rigid heat sink member. The use of gap pads or gap fillers suffer from poor thermal transfer uniformity, particularly where the group of devices to be cooled have a great degree of variance of height. Gap pads suffer from varying degrees of thermal conductivity because the thermal conductivity through the thickness of gap pad is proportional to the amount of compression of the pad. For example, the more the gap pad is compressed, the better the thermal conductivity will be. Therefore, the taller devices within a group will have greater thermal transfer to the heat sink than the shorter devices which have a less compressed gap pad between it and the heat sink member. As a result, use of a gap pad will necessarily result in non-uniform thermal transfer causing overall inferior thermal conductivity.
In view of the foregoing, there is a demand for a heat sink assembly that is capable of dissipating heat from a group of devices simultaneously. There is a demand for a heat sink assembly that can provide uniform heat dissipation for the entire group of devices to be cooled. In addition, there is a demand for a complete heat sink assembly to be able to accommodate group of devices without the use of a gap pad.
The present invention preserves the advantages of prior art heat sink assemblies for integrated circuit devices, such as microprocessors. In addition, it provides new advantages not found in currently available assemblies and overcomes many disadvantages of such currently available assemblies.
The invention is generally directed to the novel and unique heat sink assembly with particular application in cooling heat generating electronic components installed on a circuit board. The heat sink assembly of the present invention enables the simple, easy and inexpensive assembly, use and maintenance of a heat sink assembly while realizing superior heat dissipation. The heat sink of the present invention has particular application in simultaneously providing heat dissipation for a number of electronic components that may be of different sizes, shapes, configurations and heights or thicknesses.
The conforming heat sink assembly for removing heat from electronic components, having respective top surfaces defining different heights and installed on a circuit board, of the present invention is provided with a flexible thermally conductive base member with a top surface and a bottom surface. The bottom surface is adapted to be positioned in flush thermal communication with the top surfaces of each of the electronic components installed on a circuit board. A heat dissipating element is affixed to the upper surface of the flexible thermally conductive base member. The heat dissipating member is corrugated to define a number of lower contact points and upstanding fin members. The lower contact points are movable relative to one another in accordance with the top surface of the flexible thermally conductive base member. The heat dissipating element is affixed to the flexible thermally conductive base member at its lower contact points to form a conforming heat sink assembly.
For assembly and installation, the corrugated heat dissipating member is bonded to the flexible thermally conductive base member with a thermally conductive epoxy. Preferably, thermally conductive double-sided tape is adhered to each of the top surfaces of electronic components to be cooled. The base of the heat sink assembly of the present invention is then mated with the top surfaces of the components to be cooled where the base member is flexed and manipulated as needed to fully engage with the top surfaces of the components, As a result, various regions of the bottom surface of the base member may lie in different planes than one another to accommodate component top surfaces which may not lie in the same plane. When the base member is flexed and manipulated to accommodate the component top surfaces, the corrugated heat dissipating member simultaneously adjusts and flexes despite structural bonding thereto with epoxy.
It is therefore an object of the present invention to provide a heat sink assembly that can provide heat dissipation for more than one heat generating electronic component at a time.
It is an object of the present invention to provide a single heat sink assembly that can provide simultaneous heat dissipation for heat generating electronic components that have different heights or thicknesses.
It is a further object of the present invention to provide a heat sink assembly that can easily adapt to a non-uniform heat generating surface for heat dissipation therefrom.
Another object of the present invention is to provide a heat sink assembly that is lightweight.
It is a further object of the present invention to provide a heat sink assembly can be installed without additional tools.
It is yet a further object of the present invention to provide a heat sink that has an ultra light fin configuration.
Another object of present invention is to provide a heat sink assembly that is highly resistant to vibration and shock.
A further object of the present invention is to provide a heat sink assembly that has a lower center of mass and less joint stress.
Another object of the present invention is provide a heat sink assembly that has lower junction resistance and a lower overall system resistance.